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Basic overview of the debian/ directory

This article will briefly explain the different files important to the packaging of Ubuntu packages which are contained in the debian/ directory. The most important of them are debian/changelog, debian/control, debian/copyright, and debian/rules. These are required for all packages. A number of additional files in the debian/ directory may be used in order to customise and configure the behaviour of the package. Some of these files are discussed in this article, but this is not meant to be a complete list.

The changelog file

This file is a listing of the changes made in each version. It has a specific format that gives the package name, version, distribution changes, and who made the changes at a given time. The following is a template debian/changelog:

package (version) distribution; urgency=urgency
[optional blank line(s), stripped]
  * change details
    - more change details
  * even more change details
[optional blank line(s), stripped]
 -- maintainer name <email address>[two spaces]  date

package and version are the source package name and version number, respectively.

The distribution field lists the distribution(s) in which this release should be installed.

urgency describes how important an upgrade is. Its value can be one of the following: low, medium, high, emergency, or critical.

The change details consist of lines indented by at least two spaces, but these conventionally are a list. Major bullet points use an asterisk “*”, while minor bullet points are indicated by a dash “-“.

The changelog entry ends with a line indented by one space that contains the name, email of the maintainer, and date of change. The maintainer here is the one responsible for the release, but it need not be the package maintainer.

Note

If you have a signing key (see Getting set up), then make sure to use the same name and email address in debian/changelog entry as you have in your key.

Important

The date should be in RFC 5322 format, which can be obtained by using the command date -R. For convenience, the command dch may be used to edit the changelog. It will update the date automatically. For further information, see dch(1).

If you are packaging from scratch, dch --create (dch is in the devscripts package) will create a standard debian/changelog for you.

Here is a sample debian/changelog file for hello:

hello (2.8-0ubuntu1) trusty; urgency=low

 * New upstream release with lots of bug fixes and feature improvements.

-- Jane Doe <[email protected]>  Thu, 21 Oct 2013 11:12:00 -0400

Notice that the version has a -0ubuntu1 appended to it, this is the distribution revision, used so that the package can be updated (to fix bugs for example) with new uploads within the same source release version.

Ubuntu and Debian have slightly different package versioning schemes to avoid conflicting packages with the same source version. If a Debian package has been changed in Ubuntu, it has ubuntuX (where X is the Ubuntu revision number) appended to the end of the Debian version. So if the Debian hello 2.6-1 package was changed by Ubuntu, the version string would be 2.6-1ubuntu1. If a package for the application does not exist in Debian, then the Debian revision is 0 (e.g. 2.6-0ubuntu1).

For further information, see the changelog section (Section 4.4) of the Debian Policy Manual.

The control file

The debian/control file contains the information that the package manager (such as APT) uses, build-time dependencies, maintainer information, and much more. The file consists of one or more stanzas of fields, with each stanza separated by empty lines. The fields consist of key-value pairs separated by a colon “:”; conventionally, a single space follows the colon.

For the Ubuntu hello package, the debian/control file looks something like this:

Source: hello
Section: devel
Priority: optional
Maintainer: Ubuntu Developers <[email protected]>
XSBC-Original-Maintainer: Jane Doe <[email protected]>
Standards-Version: 4.6.2
Build-Depends: debhelper-compat (= 13), help2man, texinfo
Homepage: https://www.gnu.org/software/hello/

Package: hello
Architecture: any
Depends: ${misc:Depends}, ${shlibs:Depends}
Description: The classic greeting, and a good example
 The GNU hello program produces a familiar, friendly greeting. It
 allows non-programmers to use a classic computer science tool which
 would otherwise be unavailable to them. Seriously, though: this is
 an example of how to do a Debian package. It is the Debian version of
 the GNU Project's `hello world' program (which is itself an example
 for the GNU Project).

The first stanza describes the source package. It contains the following fields:

  • Source (required): The name of the source package.

  • Maintainer (required): The name and email of the package maintainer.

Note

In Ubuntu, we set the Maintainer field to a general address because anyone can change any package (this differs from Debian where changing packages is usually restricted to an individual or a team). Packages in Ubuntu should generally have the Maintainer field set to Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>. If the Maintainer field is modified, the old value should be saved in the XSBC-Original-Maintainer field. This can be done automatically with the update-maintainer script available in the ubuntu-dev-tools package. For further information, see the Debian Maintainer Field spec on the Ubuntu wiki.

  • Uploaders: The list of names and email addresses of co-maintainers.

  • Section (recommended): The application area into which the package has been classified.

  • Priority (recommended): How important the package is.

  • Build-Depends fields: Lists the packages required to build the package from source. For a full list of the

  • Standards-Version (required): The version of Debian Policy that the package complies with.

  • Homepage: The upstream home page.

  • Version Control System fields:

  • Testsuite: A comma-separated list of values allowing test execution environments to discover packages which provide tests.

  • Rules-Requires-Root: Defines whether the source package requires root access during selected targets.

Each additional stanza describes a binary package to be built. These stanzas contain the following fields:

  • Package (required): The name of the binary package.

  • Architecture (required): The architectures supported.

  • Section (recommended): The application area into which the package has been classified.

  • Priority (recommended): How important the package is.

  • Essential: Optional boolean field to prevent the package manager from removing the package when set to yes. When this field is absent, the default behaviour is no.

  • Depends fields:

  • Description (required): Contains a description of the binary package. This field consists of a synopsis and a long description.

  • Homepage: The upstream home page.

  • Built-Using: This field is used in cases where the package incorporates parts of other packages and relies on specific versions.

  • Package-Type: Indicates the type of the package, for example: deb or udeb.

For further information, see the control file section (Chapter 5) of the Debian Policy Manual.

The rules file

The debian/rules file does all the work for creating our package. It is a Makefile with targets to compile and install the application, then create the .deb file from the installed files. It also has a target to clean up all the build files so you end up with just a source package again.

More specifically, the debian/rules file has the following targets:

  • build (required)

    This target configures and compiles the package.

  • build-arch (required), build-indep (required)

    The build-arch target configures and compiles architecture-dependent binary packages (distinguished by not having the all value in the Architecture field).

    The build-indep target configures and compiles architecture-independent binary packages (distinguished by the all value for the Architecture field).

  • binary (required), binary-arch (required), binary-indep (required)

    The binary target is all that the user needs to build the binary package(s) from the source package. It is typically an empty target that depends on its two parts, binary-arch and binary-indep.

    The binary-arch target builds the binary packages which are architecture-dependent.

    The binary-indep target builds the binary packages which are architecture-independent.

  • clean (required)

    This target undoes the effects of the build and binary targets, but it does not affect output files that a binary target creates in the parent directory.

  • patch (optional)

    This target prepares the source for editing. For example, it may unpack additional upstream archives, apply patches, etc.

Here is a simplified version of the debian/rules file created by dh_make (which can be found in the dh-make package):

#!/usr/bin/make -f
# -*- makefile -*-

# Uncomment this to turn on verbose mode.
#export DH_VERBOSE=1

%:
    dh $@

Let us go through this file in some detail. What this does is pass every build target that debian/rules is called with as an argument to /usr/bin/dh, which itself will call the necessary dh_* commands.

dh runs a sequence of debhelper commands. The supported sequences correspond to the targets of a debian/rules file: build, clean, install, binary-arch, binary-indep, and binary. In order to see what commands are run in each target, run:

dh binary-arch --no-act

Commands in the binary-indep sequence are passed the “-i” option to ensure they only work on binary independent packages, and commands in the binary-arch sequences are passed the “-a” option to ensure they only work on architecture dependent packages.

Each debhelper command will record when it’s successfully run in debian/package.debhelper.log (which dh_clean deletes). So dh can tell which commands have already been run, for which packages, and skip running those commands again.

Each time dh is run, it examines the log, and finds the last logged command that is in the specified sequence. It then continues with the next command in the sequence. The --until, --before, --after, and --remaining options can override this behaviour.

If debian/rules contains a target with a name like override_dh_command, then when it gets to that command in the sequence, dh will run that target from the rules file, rather than running the actual command. The override target can then run the command with additional options, or run entirely different commands instead.

Note

To use the override feature, you should Build-Depend on debhelper version 7.0.50 or above.

Have a look at /usr/share/doc/debhelper/examples/ and dh(1) for more examples. Also see the rules section (Section 4.9) of the Debian Policy Manual.

Additional files

The install file

The install file is used by dh_install to install files into the binary package. It has two standard use cases:

  • To install files into your package that are not handled by the upstream build system

  • Splitting a single large source package into multiple binary packages.

In the first case, the install file should have one line per file installed, specifying both the file and the installation directory. For example, the following install file would install the script foo in the source package’s root directory to usr/bin and a desktop file in the debian directory to usr/share/applications:

foo usr/bin
debian/bar.desktop usr/share/applications

When a source package is producing multiple binary packages dh will install the files into debian/tmp rather than directly into debian/<package>. Files installed into debian/tmp can then be moved into separate binary packages using multiple $package_name.install files. This is often done to split large amounts of architecture independent data out of architecture dependent packages and into Architecture: all packages. In this case, only the name of the files (or directories) to be installed are needed without the installation directory. For example, foo.install containing only the architecture dependent files might look like:

usr/bin/
usr/lib/foo/*.so

While the foo-common.install containing only the architecture independent file might look like:

/usr/share/doc/
/usr/share/icons/
/usr/share/foo/
/usr/share/locale/

This would create two binary packages, foo and foo-common. Both would require their own stanza in debian/control.

See dh_install(1) and the install file section (Section 5.11) of the Debian New Maintainers’ Guide for additional details.

The watch file

The debian/watch file allows us to check automatically for new upstream versions using the tool uscan found in the devscripts package. The first line of the watch file must be the format version (4, at the time of this writing), while the following lines contain any URLs to parse. For example:

version=4
http://ftp.gnu.org/gnu/hello/hello-(.*).tar.gz

Note

If your tarballs live on Launchpad, the debian/watch file is a little more complicated (see Question 21146 and Bug 231797 for why this is). In that case, use something like:

version=4
https://launchpad.net/flufl.enum/+download http://launchpad.net/flufl.enum/.*/flufl.enum-(.+).tar.gz

Running uscan in the root source directory will now compare the upstream version number in the debian/changelog with the latest upstream version. If a new upstream version is found, it will be automatically downloaded. For example:

$ uscan
hello: Newer version (2.7) available on remote site:
    http://ftp.gnu.org/gnu/hello/hello-2.7.tar.gz
    (local version is 2.6)
hello: Successfully downloaded updated package hello-2.7.tar.gz
    and symlinked hello_2.7.orig.tar.gz to it

For further information, see uscan(1) and the watch file section (Section 4.11) of the Debian Policy Manual.

The source/format file

This file indicates the format of the source package. It should contain a single line indicating the desired format:

  • 3.0 (native) for Debian native packages (no upstream version)

  • 3.0 (quilt) for packages with a separate upstream tarball

  • 1.0 for packages wishing to explicitly declare the default format

Note

The debian/source/format file should always exist. If the file can not be found, the format 1.0 is assumed for backwards compatibility, but lintian(1) will warn you about it when you try to build a source package.

You are strongly recommended to use the newer 3.0 source format. It provides a number of new features:

  • Support for additional compression formats: bzip2, lzma and xz

  • Support for multiple upstream tarballs

  • Not necessary to repack the upstream tarball to strip the debian directory

  • Debian-specific changes are no longer stored in a single .diff.gz but in multiple patches compatible with quilt under debian/patches/. The patches to be applied automatically are listed in the debian/patches/series file.

The Debian DebSrc3.0 page summarises additional information concerning the switch to the 3.0 source package formats.

See dpkg-source(1) and the source/format section (Section 5.21) of the Debian New Maintainers’ Guide for additional details.

Additional Resources

In addition to the links to the Debian Policy Manual in each section above, the Debian New Maintainers’ Guide has more detailed descriptions of each file. Chapter 4, “Required files under the debian directory” further discusses the control, changelog, copyright and rules files. Chapter 5, “Other files under the debian directory” discusses additional files that may be used.